Negative resist composition and pattern forming method using the same

ABSTRACT

A negative resist composition, includes: (A) an alkali-soluble polymer containing a specific repeating unit as defined in the specification; (B) a crosslinking agent capable of crosslinking with the alkali soluble polymer (A) under an action of an acid; (C) a compound capable of generating an acid upon irradiation with actinic rays or radiation; (D) a specific quaternary ammonium salt as defined in the specification; and (E) an organic carboxylic acid, and a pattern forming method uses the composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a negative resist composition suitablyusable for the ultramicrolithography process such as production of VLSIor a high-capacity microchip or in other fabrication processes, and apattern forming method using the same. More specifically, the presentinvention relates to a negative resist composition capable of forming ahigh-resolution pattern by using electron beam or X-ray, and a patternforming method using the same. That is, the present invention relates toa negative resist composition for use in the process using a substratehaving thereon a specific underlying film.

2. Description of the Related Art

In the process of producing a semiconductor device such as IC and LSI,fine processing by lithography using a photoresist composition has beenconventionally performed. Recently, the integration degree of anintegrated circuit is becoming higher and formation of an ultrafinepattern in the sub-micron or quarter-micron region is required. To copewith this requirement, the exposure wavelength also tends to becomeshorter, for example, from g line to i line or further to KrF excimerlaser light. At present, other than the excimer laser light, developmentof lithography using electron beam or X-ray is proceeding.

In particular, the electron beam lithography is positioned as anext-generation or next-next-generation pattern formation technique anda negative resist assured of high sensitivity and high resolution isbeing demanded.

Also, the electron beam lithography is widely used for the preparationof a photomask employed in the semiconductor exposure because of itshigh resolution property. The process of preparing a photomask is asfollows. A shielding layer mainly comprising a shielding material suchas chromium is provided on a transparent substrate such as glasssubstrate to prepare a shielding substrate, and a resist layer is formedthereon and selectively exposed to form a resist pattern on theshielding layer. Subsequently, the shielding layer in the portion wherethe pattern is not formed is etched using the resist pattern as a maskto transfer the pattern to the shielding layer, whereby a photomaskcomprising a transparent substrate having provided thereon a shieldinglayer in a predetermined pattern can be obtained.

In the processing using an electron beam, which is a different systemfrom the block exposure of light, elevation of sensitivity is veryimportant for reducing the processing time, but in the case of anegative resist for use with an electron beam, when higher sensitivityis pursued, the line edge roughness is worsened in addition to reductionof the resolution and deterioration of the pattern profile, and a resistcapable of satisfying these properties all at the same time is stronglydemanded. The line edge roughness as used herein means that the resistedge at the interface between the pattern and the substrate irregularlyfluctuates in the direction perpendicular to the line direction due tothe resist characteristics and when the pattern is viewed from rightabove, the edge gives an uneven appearance. This unevenness istransferred by the etching step using the resist as a mask and impairsthe dimensional precision. Particularly, in the ultrafine region of 0.25μm or less, the line edge roughness is a very important problem to besolved.

Also, it is known that when a resist pattern is formed on the shieldinglayer used for the preparation of a photomask, deterioration of thepattern profile is brought about. In particular, when a negative resistis used, pattern collapse occurs due to erosion at the interface withthe substrate, giving rise to an issue that the resolving powersignificantly deteriorates, and this becomes a problem.

The high sensitivity is in a trade-off relationship with highresolution, good pattern profile and good line edge roughness and it isvery important how to satisfy these properties all at the same time.

As regards the resist suitable for the electron beam or X-raylithography process, a chemical amplification-type resist utilizing anacid catalytic reaction is mainly used in view of high sensitivity andin the case of a negative resist, a chemical amplification-type resistcomposition mainly comprising an alkali-soluble resin, a crosslinkingagent, an acid generator and an additive is being effectively used.

Various studies have been heretofore made to enhance the performance ofthe chemical amplification-type negative resist. The following studieshave been made on the additive, particularly, the ammonium salt-typeadditive. For example, JP-A-4-51243 discloses a combination of atetraalkylammonium salt and a novolak resin, JP-A-8-110638 discloses atrialkylammonium hydroxide, and JP-A-11-149159 discloses a combinationof a tetraalkylammonium salt and a polymer having a carboxylic acid inthe side chain.

However, it is impossible by any combination of these conventionallyknown compounds to satisfy high sensitivity, high resolution, goodpattern profile, good line edge roughness, and good in-vacuum PEDcharacteristic in an ultrafine region all at the same time.

Also, in JP-A-10-186660, use of an organic carboxylic acid is studied,but use of a specific resin and a specific ammonium salt is notdescribed. Furthermore, JP-A-2003-295439 sets forth use of an ammoniumsalt but is silent on use of an organic carboxylic acid. In addition,neither of these patent publications refers to improving the line edgeroughness while giving a good pattern profile with less erosion, whichis the effect of the present invention.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problems in thetechnique of enhancing performances at the fine processing of asemiconductor device or a photomask and provide a negative resistcomposition satisfying high sensitivity, high resolution, good patternprofile, good line edge roughness and good in-vacuum PED characteristicall at the same time particularly in the fine processing of asemiconductor or a photomask, where electron beam or X-ray is used, anda pattern forming method using the composition.

As a result of intensive studies, the present inventors have found thatthe object of the present invention can be attained by a negative resistcomposition using an alkali-soluble resin with a specific structure, acrosslinking agent, an acid generators an ammonium salt with a specificstructure, and an organic carboxylic acid.

That is, the present invention is as follows.

(1) A negative resist composition, comprising:

(A) an alkali-soluble polymer containing a repeating unit represented byformula (1);

(B) a crosslinking agent capable of crosslinking with the alkali solublepolymer (A) under an action of an acid;

(C) a compound Capable of generating an acid upon irradiation withactinic rays or radiation;

(D) a quaternary ammonium salt represented by formula (2); and

(E) an organic carboxylic acid:

wherein A represents a hydrogen atom, an alkyl group, a halogen atom ora cyano group;

R₁ and R₂ each independently represents a hydrogen atom, a halogen atom,an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, anaralkyl group, an alkoxy group or an alkylcarbonyloxy group; and

n represents an integer of 1 to 3;

wherein R₃ to R₆ each independently represents an alkyl group, analkenyl group, an aryl group or an aralkyl group;

B⁻ represents an OH⁻ group, a halogen atom, an R₇—CO₂ ⁻ group or anR₇—SO₃ ⁻ group; and

R₇ represents an alkyl group, an alkenyl group, an aryl group or anaralkyl group.

(2) The negative resist composition as described in

(1) above,

wherein the crosslinking agent (B) is a phenol compound having two ormore benzene rings within a molecular thereof and not containing anitrogen atom.

(3) A pattern forming method, comprising:

forming a resist film from the negative resist composition as describedin (1) or (2) above; and

exposing and developing the resist film.

Furthermore, preferred embodiments of the present invention are setforth below,

(4) The negative resist composition as described in (1) or (2) above,

wherein the alkali-soluble polymer (A) further contains at least onerepeating unit selected from the repeating units represented by formulae(3), (4) and (5):

represents any group selected from the following structures:

wherein A has the same meaning as A in formula (1);

X represents a single bond, a —COO— group, an —O— group or a —CON(R₁₆)—group;

R₁₆ represents a hydrogen atom or an alkyl group;

R₁₁ to R₁₅ each independently has the same meaning as R₁ in formula (1);

R₁₀₁ to R₁₀₆ each independently represents a hydroxy group, a halogenatom, an alkyl group, an alkoxy group, an alkylcarbonyloxy group, analkylsulfonyloxy group, an alkenyl group, an aryl group, an aralkylgroup or a carboxy group; and

a to f each independently represents an integer of 0 to 3.

(5) The negative resist composition as described in any of (1), (2) and(4) above,

wherein the crosslinking agent (B) is a phenol derivative having amolecular weight of 1,200 or less, containing from 3 to 5 benzene ringswithin a molecule thereof, and having two or more hydroxymethyl groupsor alkoxymethyl groups in total, the two or more hydroxymethyl groups oralkoxymethyl groups being bonded to at least any one benzene ring in aconcentrated manner or distributed among the benzene rings.

(6) The negative resist composition as described in any of (1), (2), (4)and (5) above,

wherein the organic carboxylic acid (E) is at least one selected fromthe group consisting of a saturated or unsaturated aliphatic carboxylicacid, an alicyclic carboxylic acid, an oxycarboxylic acid, analkoxycarboxylic acid, a ketocarboxylic acid and an aromatic carboxylicacid.

(7) The negative resist composition as described in (6) above,

wherein the organic carboxylic acid (E) is at least one selected fromthe group consisting of a benzoic acid, a 1-hydroxy-2-naphthoic acid anda 2-hydroxy-3-naphthoic acid.

DETAILED DESCRIPTION OF THE INVENTION

The negative resist composition of the present invention is described indetail below.

Incidentally, when a group (atomic group) is denoted without specifyingwhether substituted or unsubstituted, the group includes both a grouphaving no substituent and a group having a substituent. For example, an“alkyl group” includes not only an alkyl group having no substituent(unsubstituted alkyl group) but also an alkyl group having a substituent(substituted alkyl group).

[1] (A) Alkali-Soluble Polymer

The alkali-soluble polymer for use in the present invention contains arepeating unit represented by formula (1) as an essential component.

In formula (1), the alkyl group as A is preferably an alkyl group havinga carbon number of 1 to 3. Examples of the halogen atom as A include Cl,Br and F.

A is preferably a hydrogen atom or an alkyl group having a carbon numberof 1 to 3 (e.g., methyl, ethyl), more preferably a hydrogen atom or amethyl group.

Examples of the halogen atom as R₁ and R₂ include Cl, Br, F and I.

The alkyl group, alkenyl group, cycloalkyl group, aryl group, aralkylgroup, alkoxy group, alkylcarbonyloxy group or alkylsulfonyloxy group asR₁ and R₂ may have a substituent. Also, R₁ and R₂ may form a ring incooperation.

R₁ and R₂ each is independently, preferably a linear or branched alkylgroup having a carbon number of 1 to 8, which may have a substituent, analkenyl group having a carbon number of 1 to 8, which may have asubstituent, a cycloalkyl group having a carbon number of 5 to 10, whichmay have a substituent, an aryl group having a carbon number of 6 to 15,which may have a substituent, an aralkyl group having a carbon number of7 to 16, which may have a substituent, an alkoxy group having a carbonnumber of 1 to 8, which may have a substituent, or an alkylcarbonyloxygroup having a carbon number of 1 to 8, which may have a substituent.

Examples of the substituent include an alkyl group (e.g., methyl, ethyl,propyl, isopropyl, butyl, tert-butyl, hexyl), an aryl group (e.g.,phenyl, naphthyl), an aralkyl group, a hydroxyl group, an alkoxy group(e.g., methoxy, ethoxy, butoxy, octyloxy, dodecyloxy), an acyl group(e.g., acetyl, propanoyl, benzoyl) and an oxo group.

R₁ and R₂ each is independently, more preferably a hydrogen atom, ahalogen atom, an alkyl group having a carbon number of 1 to 4, which mayhave a substituent, an alkoxy group having a carbon number of 1 to 4,which may have a substituent, or an alkylcarbonyloxy group having acarbon number of 1 to 4, which may have a substituent, still morepreferably a hydrogen atom, a chlorine atom, a bromine atom, an iodineatom, an alkyl group having a carbon number of 1 to 3 (e.g., methyl,ethyl, propyl, isopropyl), or an alkoxy group having a carbon number of1 to 3 (e.g., methoxy, ethoxy, propyloxy, isopropyloxy).

The polymer as the component (A) for use in the present invention mayhave at least one repeating unit represented by formulae (3) to (5),together with the repeating unit represented by formula (1).

In formulae (3) to (5), A has the same meaning as A in formula (1), Xrepresents a single bond, a —COO— group, a —O— group, or a —CON(R₁₆)—group, R₁₆ represents a hydrogen atom or an alkyl group having a carbonnumber of 1 to 3 (e.g., methyl, ethyl, propyl). X is preferably a singlebond, —COO—, or —CON(R₁₆), more preferably a —COO— group.

R₁₁ to R₁₅ each independently has the same meaning as R₁ in formula (1).

R₁₀₁ to R₁₀₆ each independently represents a hydroxy group, a halogenatom (Cl, Br, F, I), a linear or branched alkyl group having a carbonnumber of 1 to 8, which may have a substituent, a linear or branchedalkoxy group having a carbon number of 1 to 8, a linear or branchedalkylcarbonyloxy group having a carbon number of 1 to 8, which may havea substituent, a linear or branched alkylsulfonyloxy group having acarbon number of 1 to 8, which may have a substituent, an alkenyl grouphaving a carbon number of 1 to 8, which may have a substituent, an arylgroup having a carbon number of 7 to 15, which may have a substituent,an aralkyl group having a carbon number of 7 to 16, which may have asubstituent, or a carboxy group.

Examples of the substituent thereof are the same as those of thesubstituent of R₁ in formula (1).

R₁₀₁ to R₁₀₆ each is independently, preferably a hydrogen atom, ahalogen atom, an alkyl group having a carbon number of 1 to 4, which mayhave a substituent, an alkoxy group having a carbon number of 1 to 4,which may have a substituent, or an alkylcarbonyloxy group having acarbon number of 1 to 4, which may have a substituent, more preferably ahydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkylgroup having a carbon number of 1 to 3 (e.g., methyl, ethyl, propyl,isopropyl), an alkoxy group having a carbon number of 1 to 3 (e.g.,methoxy, ethoxy, propyloxy, isopropyloxy), or an alkylcarbonyloxy grouphaving a carbon number of 1 to 3 (e.g., acetyl, propionyl).

a to f each independently represents an integer of 0 to 3.

The polymer as the component (A) for use in the present invention may beany of a resin having only one repeating unit represented by formula(1), a resin having two or more repeating units each represented byformula (1), and a resin having a repeating unit represented by formula(1) and at least one repeating unit selected from the repeating unitsrepresented by formulae (3) to (5), and other polymerizable monomerscapable of controlling the film-forming property or alkali solubilitymay be also polymerized therein.

Example of such a polymerizable monomer include, but are not limited to,styrene, an alkyl-substituted styrene, an alkoxy-substituted styrene, anO-alkylated styrene, an O-acylated styrene, a hydrogenatedhydroxystyrene, maleic anhydride, an acrylic acid derivative (e.g.,acrylic acid, acrylic acid ester), a methacrylic acid derivative (e.g.,methacrylic acid, methacrylic acid ester), an N-substituted maleimide,acrylonitrile and methacrylonitrile.

The content of the repeating unit represented by formula (1) in thepolymer as the component (A) for use in the present invention isgenerally from 50 to 100 mol %, preferably from 70 to 100 mol %.

In the polymer as the component (A), the ratio between the repeatingunit represented by formula (1) and the repeating unit(s) represented byformulae (3) to (5) is, in terms of the molar ratio, preferably from100/0 to 50/50, more preferably from 100/0 to 60/40, still morepreferably from 100/0 to 70/30.

The molecular weight of the polymer as the component (A) is, in terms ofthe weight average molecular weight, preferably from 1,000 to 200,000,more preferably from 2,000 to 50,000.

The molecular weight distribution (Mw/Mn) of the polymer as thecomponent (A) is preferably from 1.0 to 2.0, more preferably from 1.0 to1.35.

The amount added of the polymer as the component (A) is from 30 to 95mass %, preferably from 40 to 90 mass %, more preferably from 50 to 80mass %, based on the entire solid content of the composition. (In thisspecification, mass ratio is equal to weight ratio.)

Here, the molecular weight and molecular weight distribution of thepolymer are defined as a polystyrene-reduced value by the GPCmeasurement.

The polymer as the component (A) can be synthesized by a known radicalpolymerization method or anionic polymerization method. For example, inthe radical polymerization method, the vinyl monomer is dissolved in anappropriate organic solvent, and the reaction is allowed to proceed atroom temperature or under heating by using a peroxide (e.g., benzoylperoxide), a nitrile compound (e.g., azobisisobutyronitrile) or a redoxcompound (e.g., cumene hydroperoxide-ferrous salt) as the initiator,whereby the polymer can be obtained. In the anionic polymerizationmethod, the vinyl monomer is dissolved in an appropriate organicsolvent, and the reaction is allowed to proceed usually under cooling byusing a metal compound (e.g., butyllithium) as the initiator, wherebythe polymer can be obtained.

Specific examples of the alkali-soluble polymer as the component (A) foruse in the present invention are set forth below, but the presentinvention is not limited thereto.

In specific examples above, n represents a positive integer, and x, yand z represent the molar ratio of the composition. In the case of aresin comprising two components, the molar ratio is x=10 to 95 and y=5to 90, preferably x=40 to 90 and y=10 to 60, and in the case of a resincomprising three components, the molar ratio is x=10 to 90, y=5 to 85and z=5 to 85, preferably x=40 to 80, y=10 to 50 and z=10 to 50.

One of these polymers may be used alone, or two or more thereof may bemixed and used,

[2] Acid Cross-Linking Agent (Component (B))

In the present invention, a compound capable of crosslinking under theaction of an acid (hereinafter sometimes referred to as an “acidcrosslinking agent” or simply as a “crosslinking agent”) is usedtogether with the alkali-soluble polymer. A known acid crosslinkingagent can be effectively used here.

The acid crosslinking agent is preferably a compound or resin having twoor more hydroxymethyl groups, alkoxy-methyl groups, acyloxymethyl groupsor alkoxymethyl ether groups, or an epoxy compound.

More preferred examples thereof include an alkoxymethylated oracyloxymethylated melamine compound or resin, an alkoxymethylated oracyloxymethylated urea compound or resin, a hydroxymethylated oralkoxymethylated phenol compound or resin, and analkoxymethyl-etherified phenol compound or resin.

The component (B) is still more preferably a phenol derivative having amolecular weight of 1,200 or less, containing from 3 to 5 benzene ringswithin the molecule, and having two or more hydroxymethyl groups oralkoxymethyl groups in total, where the hydroxymethyl groups oralkoxymethyl groups are bonded in a concentrated manner to at least anyone benzene ring or distributed among the benzene rings. By virtue ofusing such a phenol derivative, the effects of the present invention aremore remarkably brought out.

The alkoxymethyl group bonded to the benzene ring is preferably analkoxymethyl group having a carbon number of 6 or less, specifically, amethoxymethyl group, an ethoxymethyl group, an n-propoxymethyl group, ani-propoxymethyl group, an n-butoxymethyl group, an i-butoxymethyl group,a sec-butoxymethyl group, or a tert-butoxymethyl group. Analkoxy-substituted alkoxy group such as 2-methoxyethoxy group and2-methoxy-1-propyl group is also preferred.

The crosslinking agent (B) is preferably a phenol compound having two ormore benzene rings within the molecule and containing no nitrogen atom.

Out of these phenol derivatives, particularly preferred compounds areset forth below.

(wherein L¹ to L⁸ may be the same or different and each represents ahydroxymethyl group, a methoxymethyl group or an ethoxymethyl group).

The phenol derivative having a hydroxymethyl group can be obtained byreacting a corresponding phenol compound having no hydroxymethyl group(a compound where in the formulae above, L¹ to L⁸ each is a hydrogenatom) with formaldehyde in the presence of a base catalyst. At thistime, in order to prevent resinification or gelling, the reaction ispreferably performed at a temperature of 60° C. or less. Specifically,this phenol derivative can be synthesized by the method described, forexample, in JP-A-6-282067 and JP-A-7-64285.

The phenol derivative having an alkoxymethyl group can be obtained byreacting a corresponding phenol derivative having a hydroxymethyl groupwith an alcohol in the presence of an acid catalyst. At this time, inorder to prevent resinification or gelling, the reaction is preferablyperformed at a temperature of 100° C. or less. Specifically, this phenolderivative can be synthesized by the method described, for example, inEP-A-632003.

The thus-synthesized phenol derivative having a hydroxymethyl group oran alkoxymethyl group is preferred in view of stability during storage,but a phenol derivative having an alkoxymethyl group is particularlypreferred in view of stability during storage.

One of these phenol derivatives having two or more hydroxymethyl groupsor alkoxymethyl groups in total bonded in a concentrated manner to atleast any one benzene ring or distributed among the benzene rings may beused alone, or two or more thereof may be used in combination.

Preferred examples of the crosslinking agent further include (i) acompound having an N-hydroxymethyl group, an N-alkoxymethyl group or anN-acyloxymethyl group, and (ii) an epoxy group, which are describedbelow.

Examples of the (i) compound having an N-hydroxymethyl group, anN-alkoxymethyl group or an N-acyloxymethyl group include monomers,oligomer-melamine-formaldehyde condensates and urea-formaldehydecondensates disclosed in EP-A-0133216 and West German Patent Nos.3,634,671 and 3,711,264, and alkoxy-substituted compounds andbenzoguanamine-formaldehyde condensates disclosed in EP-A-0212482.

More preferred examples include a melamine-formaldehyde derivativehaving at least two free N-hydroxymethyl groups, N-alkoxymethyl groupsor N-acyloxymethyl groups, with an N-alkoxymethyl derivative being stillmore preferred.

The (ii) epoxy compound includes a monomer-, dimer-, oligomer- orpolymer-form epoxy compound containing one or more epoxy groups.Examples thereof include a reaction product of bisphenol A andepichlorohydrin, and a reaction product of low molecular weightphenol-formaldehyde resin and epichlorohydrin. Other examples includeepoxy resins described and used in U.S. Pat. No. 4,026,705 and BritishPatent 1,539,192.

The crosslinking agent is preferably added in an amount of 3 to 65 mass%, more preferably from 5 to 50 mass %. When the amount of thecrosslinking agent added is from 3 to 65 mass %, reduction in theresidual film ratio and resolving power can be prevented and at the sametime, good stability of the resist solution can be maintained duringstorage.

In the present invention, one crosslinking agent may be used alone, ortwo or more kinds of crosslinking agents may be used in combination.

For example, in the case of using other crosslinking agents such as (i)and (ii) above in addition to the phenol derivative, the ratio betweenthe phenol derivative and the other crosslinking agent is, in terms ofthe molar ratio, from 100/0 to 20/80, preferably from 90/10 to 40/60,more preferably from 80/20 to 50/50.

[3] Compound Capable of Generating an Acid Upon Irradiation with ActinicRays or Radiation (Component (C))

The negative resist composition of the present invention comprises acompound capable of generating an acid upon irradiation with actinicrays or radiation (hereinafter sometimes referred to as an “acidgenerator”).

The acid generator which can be used may be appropriately selected froma photoinitiator for photo-cationic polymerization, a photoinitiator forphotoradical polymerization, a photo-decoloring agent for coloringmatters, a photo-discoloring agent, a compound known to generate an acidupon irradiation with actinic rays or radiation and used for microresistor the like, and a mixture thereof.

Examples thereof include a diazonium salt, a phosphonium salt, asulfonium salt, an iodonium salt, imidosulfonate, oxime sulfonate,diazodisulfone, disulfone and o-nitrobenzyl sulfonate.

Also, a compound where a group or compound capable of generating an acidupon irradiation with actinic rays or radiation is introduced into themain or side chain of a polymer, such as compounds described in U.S.Pat. No. 3,849,137, German Patent 3,914,407, JP-A-63-26653,JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452,JP-A-62-153853 and JP-A-63-146029, may be used.

Furthermore, compounds capable of generating an acid by the effect oflight described, for example, in U.S. Pat. No. 3,779,778 and EuropeanPatent 126,712 may also be used.

Out of the compounds capable of decomposing upon irradiation withactinic rays or radiation to generate an acid, the compounds representedby the following formulae (ZI), (ZII) and (ZIII) are preferred.

In formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents anorganic group.

X⁻ represents a non-nucleophilic anion, and preferred examples thereofinclude sulfonate anion, carboxylate anion, bis(alkylsulfonyl)amideanion, tris(alkylsulfonyl)methide anion, BF₄ ⁻, PF₆ ⁻ and SbF₆ ⁻. Theanion is preferably an organic anion containing a carbon atom.

The preferred organic anion includes organic anions represented by thefollowing formulae (AN1) to (AN4):

In formulae (AN1) and (AN2), Rc₁ represents an organic group.

The organic group in Rc₁ includes an organic group having a carbonnumber of 1 to 30 and is preferably an alkyl or aryl group which may besubstituted, or a group where a plurality of such groups are connectedthrough a single bond or a linking group such as —O—, —CO₂—, —S—, —SO₃—and —SO₂N(Rd₁)-.

Rd₁ represents a hydrogen atom or an alkyl group and may form a ringstructure together with the alkyl or aryl group to which Rd₁ is bonded.

The organic group of Rc₁ is more preferably an alkyl group substitutedby a fluorine atom or a fluoroalkyl group at the 1-position, or a phenylgroup substituted by a fluorine atom or a fluoroalkyl group. By virtueof having a fluorine atom or a fluoroalkyl group, the acidity of theacid generated upon irradiation with light increases and the sensitivityis enhanced. When Rc₁ has 5 or more carbon atoms, at least one carbonatom is preferably such that a part of hydrogen atoms remain withoutreplacing all hydrogen atoms by a fluorine atom, and more preferablysuch that the number of hydrogen atoms is larger than the number offluorine atoms. The absence of a perfluoroalkyl group having a carbonnumber of 5 or more enables reduction in the toxicity to ecology.

The most preferred embodiment of Rc₁ is a group represented by thefollowing formula.

In the formula, Rc₆ represents a perfluoroalkylene group having a carbonnumber of 4 or less, preferably from 2 to 4, more preferably 2 or 3, ora phenylene group substituted by from 1 to 4 fluorine atoms and/or from1 to 3 fluoroalkyl groups.

Ax represents a single bond or a divalent linking group (preferably —O—,—CO₂—, —S—, —SO₃— or —SO₂N(Rd₁)-). Rd₁ represents a hydrogen atom or analkyl group and may combine with Rc₇ to form a ring structure.

Rc₇ represents a hydrogen atom, a fluorine atom, a linear or branchedalkyl group which may be substituted, a monocyclic or polycycliccycloalkyl group which may be substituted, or an aryl group which may besubstituted. The alkyl group, cycloalkyl group and aryl group, whicheach may be substituted, preferably contain no fluorine atom as thesubstituent.

In formulae (AN3) and (AN4), Rc₃, Rc₄ and Rc₅ each independentlyrepresents an organic group.

The preferred organic groups for Rc₃, Rc₄ and Rc₅ in formulae (AN3) and(AN4) are the same as the preferred organic groups in Rc₁.

Rc₃ and Rc₄ may combine to form a ring.

The group formed by combining Rc₃ and Rc₄ includes an alkylene group andan arylene group and is preferably a perfluoroalkylene group having acarbon number of 2 to 4. When Rc₃ and Rc₄ combine to form a ring, theacidity of the acid generated upon irradiation with light increases andthis is preferred because the sensitivity is enhanced.

The carbon number of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ in formula(ZI) is generally from 1 to 30, preferably from 1 to 20.

Two members out of R₂₀₁ to R₂₀₃ may combine to form a ring structure,and the ring may contain an oxygen atom, a sulfur atom, an ester bond,an amide bond or a carbonyl group.

Examples of the group formed by combining two members out of R₂₀₁, toR₂₀₃ include an alkylene group (e.g., butylene, pentylene).

Specific examples of the organic group as R₂₀₁, R₂₀₂ and R₂₀₃ includecorresponding groups in the compounds (ZI-1), (ZI-2) and (ZI-3) whichare described later.

The compound may be a compound having a plurality of structuresrepresented by formula (ZI). For example, the compound may be a compoundhaving a structure where at least one of R₂₀₁ to R₂₀₃ in a compoundrepresented by formula (ZI) is bonded to at least one of R₂₀₁ to R₂₀₃ inanother compound represented by formula (ZI).

The component (ZI) is more preferably a compound (ZI-1), (ZI-2) or(ZI-3) described below.

The compound (ZI-1) is an arylsulfonium compound where at least one ofR₂₀₁ to R₂₀₃ in formula (ZI) is an aryl group, that is, a compoundhaving an arylsulfonium as the cation.

In the arylsulfonium compound, R₂₀₁ to R₂₀₃ all may be an aryl group ora part of R₂₀₁ to R₂₀₃ may be an aryl group with the remaining being analkyl group or a cycloalkyl group.

Examples of the arylsulfonium compound include a triarylsulfoniumcompound, a diarylalkylsulfonium compound, an aryldialkylsulfoniumcompound, a diarylcycloalkylsulfonium compound, and anaryldicycloalkylsulfonium compound.

The aryl group in the arylsulfonium compound is preferably an aryl groupsuch as phenyl group and naphthyl group, or a heteroaryl group such asindole residue and pyrrole residue, more preferably a phenyl group or anindole residue. In the case where the arylsulfonium compound has two ormore aryl groups, these two or more aryl groups may be the same ordifferent.

The alkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a linear or branched alkyl group having a carbonnumber of 1 to 15, and examples thereof include a methyl group, an ethylgroup, a propyl group, an n-butyl group, a sec-butyl group and atert-butyl group.

The cycloalkyl group which is present, if desired, in the arylsulfoniumcompound is preferably a cycloalkyl group having a carbon number of 3 to15, and examples thereof include a cyclopropyl group, a cyclobutyl groupand a cyclohexyl group.

The aryl group, alkyl group and cycloalkyl group of R₂₀₁ to R₂₀₃ eachmay have, as the substituent, an alkyl group (for example, an alkylgroup having a carbon number of 1 to 15), a cycloalkyl group (forexample, a cycloalkyl group having a carbon number of 3 to 15), an arylgroup (for example, an aryl group having a carbon number of 6 to 14), analkoxy group (for example, an alkoxy group having a carbon number of 1to 15), a halogen atom, a hydroxyl group or a phenylthio group. Thesubstituent is preferably a linear or branched alkyl group having acarbon number of 1 to 12, a cycloalkyl group having a carbon number of 3to 12, or a linear, branched or cyclic alkoxy group having a carbonnumber of 1 to 12, more preferably an alkyl group having a carbon numberof 1 to 4 or an alkoxy group having a carbon number of 1 to 4. Thesubstituent may be substituted to any one of three members R₂₀₁ to R₂₀₃or may be substituted to all of these three members. In the case whereR₂₀₁ to R₂₀₃ are an aryl group, the substituent is preferablysubstituted at the p-position of the aryl group.

The compound (ZI-2) is described below.

The compound (ZI-2) is a compound where R₂₀₁ to R₂₀₃ in formula (ZI)each independently represents an aromatic ring-tree organic group. Thearomatic ring as used herein includes an aromatic ring containing aheteroatom.

The aromatic ring-free organic group as R₂₀₁ to R₂₀₃ generally has acarbon number of 1 to 30, preferably from 1 to 20.

R₂₀₁ to R₂₀₃ each is independently preferably an alkyl group, acycloalkyl group, an allyl group or a vinyl group, more preferably alinear, branched or cyclic 2-oxoalkyl group or an alkoxycarbonylmethylgroup, still more preferably a linear or branched 2-oxoalkyl group.

The alkyl group as R₂₀₁ to R₂₀₃ may be either linear or branched and ispreferably a linear or branched alkyl group preferably having a carbonnumber of 1 to 10 (e.g., methyl, ethyl, propyl, butyl, pentyl). Thealkyl group as R₂₀₁ to R₂₀₃ is more preferably a linear or branched2-oxoalkyl group or an alkoxycarbonylmethyl group.

The cycloalkyl group as R₂₀₁ to R₂₀₃ is preferably a cycloalkyl grouphaving a carbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl,norbornyl).

The cycloalkyl group as R₂₀₁ to R₂₀₃ is more preferably a cyclic2-oxoalkyl group.

The 2-oxoalkyl group as R₂₀₁ to R₂₀₃ may be linear, branched or cyclicand is preferably a group having >C═O at the 2-position of theabove-described alkyl or cycloalkyl group.

The alkoxy group in the alkoxycarbonylmethyl group as R₂₀₁ to R₂₀₃ ispreferably an alkoxy group preferably having a carbon number of 1 to 5(e.g., methoxy, ethoxy, propoxy, butoxy, pentoxy).

R₂₀₁ to R₂₀₃ each may be further substituted by a halogen atom, analkoxy group (for example, an alkoxy group having a carbon number of 1to 5), a hydroxyl group, a cyano group or a nitro group.

The compound (ZI-3) is a compound represented by the following formula(ZI-3), and this is a compound having a phenacylsulfonium saltstructure.

In formula (ZI-3), R_(1c) to R_(5c) each independently represents ahydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group or ahalogen atom.

R_(6c) and R_(7c) each independently represents a hydrogen atom, analkyl group or a cycloalkyl group.

R_(x) and R_(y) each independently represents an alkyl group, acycloalkyl group, an allyl group or a vinyl group.

Any two or more members out of R_(1c) to R_(7c) or a pair of R_(x) andR_(y) may combine with each other to form a ring structure, and the ringstructure may contain an oxygen atom, a sulfur atom, an ester bond or anamide bond. Examples of the group formed by combining any two or moremembers out of R_(1c) to R_(7c) or a pair of R_(x) and R_(y) include abutylene group and a pentylene group.

X⁻ represents a non-nucleophilic anion, and examples thereof are thesame as those of the non-nucleophilic anion of X⁻ in formula (ZI).

The alkyl group as R_(1c) to R_(7c) may be linear or branched and is,for example, an alkyl group having a carbon number of 1 to 20,preferably a linear or branched alkyl group having a carbon number of 1to 12 (for example, a methyl group, an ethyl group, a linear or branchedpropyl group, a linear or branched butyl group, or a linear or branchedpentyl group).

The cycloalkyl group as R_(1c) to R_(7c) is preferably a cycloalkylgroup having a carbon number of 3 to 8 (e.g., cyclopentyl, cyclohexyl).

The alkoxy group as R_(1c) to R_(5c) may be linear, branched or cyclicand is, for example, an alkoxy group having a carbon number of 1 to 10,preferably a linear or branched alkoxy group having a carbon number of 1to 5 (for example, a methoxy group, an ethoxy group, a linear orbranched propoxy group, a linear or branched butoxy group, or a linearor branched pentoxy group), or a cyclic alkoxy group having a carbonnumber of 3 to 8 (e.g., cyclopentyloxy, cyclohexyloxy).

A compound where any one of R_(1c) to R_(5c) is a linear or branchedalkyl group, a cycloalkyl group, or a linear, branched or cyclic alkoxygroup is preferred, and a compound where the sum of carbon numbers ofR_(1c) to R_(5c) is from 2 to 15 is more preferred. By virtue of thisconstruction, the solvent solubility is more enhanced and generation ofparticles during storage is suppressed.

The alkyl group as R_(x) and R_(y) is the same as the alkyl group ofR_(1c) to R_(7c). The alkyl group as R_(x) and R_(y) is preferably alinear or branched 2-oxoalkyl group or an alkoxycarbonylmethyl group.

The linear, branched or cyclic 2-oxoalkyl group includes a grouphaving >C═O at the 2-position of the alkyl group or cycloalkyl group asR_(1c) to R_(7c).

The alkoxy group in the alkoxycarbonylmethyl group is the same as thealkoxy group of R_(1c) to R_(5c).

R_(x) and R_(y) each is preferably an alkyl group having a carbon numberof 4 or more, more preferably 6 or more, still more preferably 8 ormore.

In formulae (ZII) and (ZIII), R₂₀₄ to R₂₀₇ each independently representsan aryl group which may have a substituent, an alkyl group which mayhave a substituent, or a cycloalkyl group which may have a substituent.

The aryl group of R₂₀₄ to R₂₀₇ is preferably a phenyl group or anaphthyl group, more preferably a phenyl group.

The alkyl group of R₂₀₄ to R₂₀₇ may be linear or branched and ispreferably a linear or branched alkyl group having a carbon number of 1to 10 (e.g., methyl, ethyl, propyl, butyl, pentyl).

The cycloalkyl group of R₂₀₄ to R₂₀₇ is preferably a cycloalkyl grouphaving a carbon number of 3 to 10 (e.g., cyclopentyl, cyclohexyl,norbornyl).

Examples of the substituent which R₂₀₄ to R₂₀₇ each may have include analkyl group (for example, an alkyl group having a carbon number of 1 to15), a cycloalkyl group (for example, a cycloalkyl group having a carbonnumber of 3 to 15), an aryl group (for example, an aryl group having acarbon number of 6 to 15), an alkoxy group (for example, an alkoxy grouphaving a carbon number of 1 to 15), a halogen atom, a hydroxyl group anda phenylthio group.

X⁻ represents a non-nucleophilic anion and is the same as thenon-nucleophilic anion of X⁻ in formula (ZI).

Out of the compounds capable of generating an acid upon irradiation withactinic rays or radiation, preferred compounds further include thecompounds represented by the following formulae (ZIV), (ZV) and (ZVI):

In formulae (ZIV) to (ZVI), Ar₃ and Ar₄ each independently represents asubstituted or unsubstituted aryl group.

R₂₀₈ represents a substituted or unsubstituted alkyl group, asubstituted or unsubstituted cycloalkyl group, or a substituted orunsubstituted aryl group.

R₂₀₉ and R₂₁₀ each represents a substituted or unsubstituted alkylgroup, a substituted or unsubstituted cycloalkyl group, a substituted orunsubstituted aryl group, or an electron-withdrawing group. R₂₀₉ ispreferably a substituted or unsubstituted aryl group, and R₂₁₀ ispreferably an electron-withdrawing group, more preferably a cyano groupor a fluoroalkyl group.

A represents a substituted or unsubstituted alkylene group, asubstituted or unsubstituted alkenylene group, or a substituted orunsubstituted arylene group.

Among the compounds capable of generating an acid upon irradiation withactinic rays or radiation, the compounds represented by formulae (ZI) to(ZIII) are preferred, the compounds represented by formulae (ZI) and(ZII) are more preferred, and the compounds represented by formulae(ZI-1) to (ZI-3) are still more preferred.

Furthermore, a compound capable of generating an acid represented by anyone of the following formulae (AC1) to (AC3) upon irradiation withactinic rays or radiation is preferred.

That is, a preferred acid generator is a compound where in the structureof formula (ZI), X⁻ is an anion selected from formulae (AN1), (AN3) and(AN4), and a more preferred compound is a compound where X⁻ is an anionselected from formulae (AN3) and (AN4).

Out of the compounds capable of decomposing upon irradiation withactinic rays or radiation to generate an acid, particularly preferredexamples are set forth below.

One of these acid generators may be used alone, or two or more kindsthereof may be used in combination. In the case of using two or morekinds in combination, compounds capable of generating two or more kindsof organic acids differing in the total number of atoms except forhydrogen atom by 2 or more are preferably combined.

The content of the acid generator in the composition is preferably from0.1 to 20 mass %, more preferably from 0.5 to 10 mass %, still morepreferably from 1 to 7 mass %, based on the entire solid content of thenegative resist composition.

[4] Quaternary Ammonium Salt Represented by Formula (2) (Component (D))

The alkyl group, alkenyl group, aryl group and aralkyl group as R₃ to R₆in formula (2) each may have a substituent. Also, two or more groups outof R₃ to R₆ may combine to form an alicyclic or aromatic ring.

R₃ to R₆ each is preferably a linear or branched alkyl group having acarbon number of 1 to 30, a linear or branched alkenyl group having acarbon number of 1 to 30, an aryl group having a carbon number of 6 to18, an aralkyl group having a carbon number of 7 to 18, or a groupcomprising a combination of these groups.

These groups each may have a substituent, and examples of thesubstituent include the same as those of the substituent of R₁ informula (1), and a hydroxyl group. Furthermore, these groups each mayhave therein a linking group such as ether group, ester group and amidegroup.

R₃ to R₆ each is more preferably a linear or branched alkyl group havinga carbon number of 1 to 25, or a linear or branched alkenyl group havinga carbon number of 1 to 25, still more preferably a linear or branchedalkyl group having a carbon number of 1 to 20.

In the R₇CO₂ ⁻ group and R₇—SO₃ ⁻ group as B⁻, R₇ preferably representsa linear or branched alkyl group having a carbon number of 1 to 8, alinear or branched alkenyl group having a carbon number of 1 to 8, anaryl group having a carbon number of 6 to 18, or an aralkyl group havinga carbon number of 7 to 18.

B⁻ is preferably an OH⁻ group, a halogen atom (e.g., chlorine, bromine,iodine, fluorine), or an R₇—CO₂— group (wherein R₇ is preferably analkyl group having a carbon number of 1 to 12, more preferably from 1 to6), more preferably an OH group, a halogen atom (e.g., chlorine,bromine, iodine, fluorine, or an R₇—CO₂ ⁻ group (wherein R₇ is an alkylgroup having a carbon number of 1 to 4).

Specific preferred examples of the component (D) are set forth below,but the present invention is not limited thereto.

The content of the component (D) for use in the present invention ispreferably from 0.01 to 10 mass %, more preferably from 0.03 to 5 mass%, still more preferably from 0.05 to 3 mass %, based on the solidcontent of the entire negative resist composition.

In the present invention, one of the quaternary ammonium salts as thecomponent (D) may be used alone, or two or more kinds thereof may bemixed and used.

[5] Organic Carboxylic Acid (Component (E))

The organic carboxylic compound as the component (E) is not particularlylimited and, for example, a saturated or unsaturated aliphaticcarboxylic acid, an alicyclic carboxylic acid, an oxycarboxylic acid, analkoxycarboxylic acid, a ketocarboxylic acid, and an aromatic carboxylicacid all may be used. Examples thereof include a monovalent orpolyvalent aliphatic carboxylic acid such as formic acid, acetic acid,propionic acid, butyric acid, isobutyric acid, oxalic acid, malonicacid, succinic acid, glutaric acid and adipic acid, an alicycliccarboxylic acid such as 1,1-cyclohexanedicarboxylic acid,1,2-cyclohexane-dicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid and 1,1-cyclohexyldiacetic acid, anunsaturated aliphatic carboxylic acid such as acrylic acid, crotonicacid, isocrotonic acid, 3-butenoic acid, methacrylic acid, 4-pentenoicacid, propiolic acid, 2-butenoic acid, maleic acid, fumaric acid andacetylene carboxylic acid, an oxycarboxylic acid such as oxyacetic acid,an alkoxycarboxylic acid such as methoxyacetic acid and ethoxyaceticacid, a ketocarboxylic acid such as pyruvic acid, a benzoic acid, ap-hydroxybenzoic acid, an o-hydroxybenzoic acid, a2-hydroxy-3-nitrobenzoic acid, a 3,5-dinitrobenzoic acid, a2-nitrobenzoic acid, a 2,4-dinitrobenzoic acid, a 2,5-dinitrobenzoicacid, a 2,6-dinitrobenzoic acid, a 3,5-dinitrobenzoic acid, a2-vinylbenzoic acid, a 4-vinylbenzoic acid, a phthalic acid, aterephthalic acid, an isophthalic acid, a 2-naphthoic acid, a1-hydroxy-2-naphthoic acid, and a 2-hydroxy-3-naphthoic acid. In thepresent invention, at the time of forming a pattern by using an electronbeam in vacuum, the organic carboxylic acid may vaporize from the resistfilm surface to contaminate the imaging chamber, and for this reason,the preferred compound is an organic carboxylic acid having an aromatic.Above all, for example, a benzoic acid, a 1-hydroxy-2-naphthoic acid anda 2-hydroxy-3-naphthoic acid are more preferred.

One of these organic carboxylic acids may be use alone, or two or morekinds thereof may be used in combination.

The amount of the organic carboxylic acid (E) blended is preferably from0.01 to 10 parts by mass, more preferably from 0.01 to 5 parts by mass,still more preferably from 0.01 to 3 parts by mass, per 100 parts bymass of the alkali-soluble polymer (A).

Also, the blending ratio between the quaternary ammonium salt as thecomponent (D) and the organic carboxylic acid as the component (E) ispreferably (D)/(E)=5 to 95/95 to 5 (by mass), more preferably (D)/(E)=10to 90/90 to 10 (by mass).

The negative resist composition of the present invention may furthercontain, if desired, a known compound such as nitrogen-containingorganic basic compound, dye, surfactant, photolyzable base compound andphoto-base generator. Examples of these compounds include respectivecompounds described in JP-A-2002-6500.

Also, examples of the solvent for use in the negative resist compositionof the present invention include solvents described similarly inJP-A-2002-6500.

Preferred examples of the solvent include ethylene glycol monoethylether acetate, cyclohexanone, 2-heptanone, propylene glycol monomethylether, propylene glycol monomethyl ether acetate, propylene glycolmonomethyl ether propionate, propylene glycol monoethyl ether acetate,methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methylβ-methoxyisobutyrate, ethyl butyrate, propyl butyrate, methyl isobutylketone, ethyl acetate, isoamyl acetate, ethyl lactate, toluene, xylene,cyclohexyl acetate, diacetone alcohol, N-methylpyrrolidone,N,N-dimethylformamide, γ-butyrolactone, N,N-dimethylacetamide, propylenecarbonate and ethylene carbonate. One of these solvents may be usedalone, or some may be used in combination.

The solid materials of the resist composition preferably dissolve in thesolvent described above to a solid material concentration of 1 to 40mass %, more preferably from 1 to 30 mass %, still more preferably from3 to 20 mass %.

The negative resist composition of the present invention is coated on asubstrate to form a thin film. The thickness of this coated film ispreferably from 0.05 to 4.0 μm.

In the present invention, a commercially available inorganic or organicantireflection film may be used, if desired. Furthermore, anantireflection film may be used by coating it on the resist upper layer.As for this antireflection film, the antireflection film described inJP-A-2002-6500 may be used.

The use mode of the negative resist composition of the present inventionis described below.

For example, in the production of a precision integrated circuit device,the step of forming a pattern on a resist film comprises coating thenegative resist composition of the present invention directly on asubstrate (for example, a silicon/silicon dioxide film, a glasssubstrate, a metal substrate, a silicon nitride substrate, a titaniumnitride substrate or a chromium oxide substrate) or on an antireflectionfilm previously provided by coating on the substrate, irradiating thecoated film with radiation or actinic rays from a light source directlyor through a mask, and subjecting the resist film to heating,development, rinsing and drying, whereby a good resist pattern can beformed. In the present invention, the substrate is preferably asubstrate except for silicon (bare silicon), more preferably a substratehaving provided on the surface thereof a metal deposition film or ametal-containing film, still more preferably a substrate on whichsurface a vapor deposition film by Cr, Mo, MoSi, TaSi or an oxide ornitride thereof or a film containing Cr, Mo, MoSi, TaSi or an oxide ornitride thereof is provided, yet still more preferably a substrate onwhich surface a vapor deposition film by Cr, MoSi, TaSi or an oxide ornitride thereof is provided.

The light source is preferably a light source emitting light at awavelength of 150 to 250 nm (specifically, a KrF excimer laser (248 nm),an ArF excimer laser (193 nm), or an F2 excimer laser (157 nm)), anelectron beam or an X-ray. In the present invention, a device using anexposure light source emitting an electron beam or an X-ray is mostpreferred.

The developer used for the negative resist composition of the presentinvention may be a known developer, and examples thereof include adeveloper described in JP-A-2002-6500.

EXAMPLES

The present invention is described in greater detail below by referringto Examples, but the present invention should not be construed as beinglimited thereto.

1. Synthesis Example of Constituent Material (1) Alkali-Soluble Polymer(Component A) Synthesis Example 1 Synthesis of Resin (29))

4-Acetoxystyrene (3.9 g (0.024 mol)) and 0.8 g (0.006 mol) of4-methoxystyrene were dissolved in 30 ml of 1-methoxy-2-propanol, andunder stirring in a nitrogen stream, 70 ml of a 1-methoxy-2-propanolsolution containing 50 mg of 2,21-azobis(2,4-dimethylvaleronitrile)(V-65, trade name, produced by Wako Pure Chemical Industries, Ltd.) as apolymerization initiator, 9.1 g (0.056 mol) of 4-acetoxystyrene and 1.9g (0.014 mol) of 4-methoxystyrene was added dropwise thereto at 70° C.over 2 hours. After 2 hours, 50 mg of the initiator was added, and thereaction was further allowed to proceed for 2 hours. Thereafter, thetemperature was raised to 90° C., and the stirring was continued for 1hour. The obtained reaction solution was allowed to cool and then pouredinto 1 liter of ion-exchanged water with vigorous stirring toprecipitate a white resin. The resin obtained was dried and thendissolved in 100 ml of methanol and after adding 25% tetramethylammoniumhydroxide to hydrolyze the acetoxy group in the resin, the resultingsolution was neutralized with an aqueous hydrochloric acid solution toprecipitate a white resin. This resin was washed with ion-exchangedwater and dried under reduced pressure to obtain 11.6 g of Resin (29) ofthe present invention. The obtained resin was measured for the molecularweight by GPC and found to have a weight average molecular weight (Mw,in terms of polystyrene) of 9,200 and a dispersity (Mw/Mn) of 2.0.

The polymers as the component (A) for use in the present invention weresynthesized in the same manner.

(2) Synthesis of Crosslinking Agent (Component B) Synthesis of (HM-1):

1-[α-Methyl-α-(4-hydroxyphenyl)ethyl]-4-[α,α-bis(4-hydroxyphenyl)ethyl]benzene(Trisp-PA manufactured by Honshu Chemical Industry Co., Ltd.) (20 g) wasadded to an aqueous 10% potassium hydroxide solution and dissolved withstirring, and while stirring this solution, 60 ml of an aqueous 37%formalin solution was gradually added thereto at room temperature over 1hour. After further stirring at room temperature for 6 hours, thesolution was poured into an aqueous dilute sulfuric acid solution, andthe precipitate formed was collected by filtration, thoroughly washedwith water and then recrystallized from 30 ml of methanol to obtain 20 gof white powder of Hydroxymethyl Group-Containing Phenol Derivative[HM-1] having a structure shown below. The purity was 92% (as determinedby a liquid chromatography method).

Synthesis of (MM-1):

Hydroxymethyl Group-Containing Phenol Derivative [HM-1] (20 g) obtainedin synthesis Example above was added to 1 liter of methanol anddissolved under heating with stirring. Subsequently, 1 ml ofconcentrated sulfuric acid was added to the resulting solution, and themixture was refluxed under heating for 12 hours. After the completion ofreaction, the reaction solution was cooled, and 2 g of potassiumcarbonate was added thereto. This mixture was sufficiently concentrated,and 300 ml of ethyl acetate was added thereto. The resulting solutionwas washed with water and then concentrated to dryness to obtain 22 g ofa white solid of Methoxymethyl Group-Containing Phenol Derivative [MM-1]having a structure shown below. The purity thereof was 90% (asdetermined by a liquid chromatography method).

Furthermore, the phenol derivatives shown below were synthesized in thesame manner.

2. Examples Example 1 (1) Preparation and Coating of Negative ResistCoating Solution

(Composition of Negative Resist Coating Solution) Component (A): Resin(29) 0.40 g Component (B): Crosslinking Agent MM-1 0.12 g Component (C):Acid Generator C-1 0.05 g Component (D): Ammonium Salt D-1 0.002 g Component (E): Organic Carboxylic Acid 0.012 g  E-1

The coating solution composition above was dissolved in 9.0 g ofpropylene glycol monomethyl ether acetate, and 0.001 g of PF6320(produced by OMNOVA, hereinafter simply referred to as “W-1”) as asurfactant was added thereto and dissolved. The obtained solution wasmicrofiltered through a membrane filter having a pore size of 0.1 μm toobtain a resist solution.

This resist solution was coated using a spin coater, Mark 8,manufactured by Tokyo Electron Ltd. on a 6-inch wafer having thereon Croxide vapor-deposited by the same processing as the shielding film usedfor a photomask, and dried at 110° C. for 90 seconds on a hot plate toobtain a resist film having a thickness of 0.3 μm.

(2) Production of Negative Resist Pattern

This resist film was subjected to pattern irradiation using an electronbeam imaging device (HL750 manufactured by Hitachi, Ltd., acceleratingvoltage: 50 KeV). After the irradiation, the resist film was heated at120° C. for 90 seconds on a hot plate, dipped in an aqueous 2.38 mass %tetramethylammonium hydroxide (TMAH) solution for 60 seconds, rinsedwith water for 30 seconds and dried. The obtained pattern was evaluatedfor the sensitivity, resolving power, pattern profile and line edgeroughness by the following methods.

(2-1) Sensitivity

The cross-sectional profile of the pattern obtained was observed byusing a scanning electron microscope (S-4300, manufactured by Hitachi,Ltd.), and the exposure dose necessary for resolving a 0.15-μm line(line:space=1:1) was defined as the sensitivity.

(2-2) Resolving Power

The limiting resolving power (the line and space were separated andresolved) at the exposure dose giving the sensitivity above was definedas the resolving power.

(2-3) Pattern Profile

The cross-sectional profile of a 0.15-μm line pattern at the exposuredose giving the sensitivity above was observed by a scanning electronmicroscope (S-4300, manufactured by Hitachi, Ltd.) and rated on athree-point scale of rectangular, slightly eroded, and eroded.

(2-4) Line Edge Roughness

The line width was measured at arbitrary 30 points in the region of 50μm in the longitudinal direction of a 0.15-μm line pattern at theirradiation dosage giving the sensitivity above, and the variationthereof was evaluated by 3σ.

(2-5) In-Vacuum PED Characteristics

The wafer was set in a vacuum chamber and irradiated with an electronbeam at the irradiation dose giving the sensitivity above, andimmediately or 3 hours after the irradiation, the wafer was baked(heat-treated) at 120° C. for 90 seconds and then developed as describedabove to obtain a line pattern.

With respect to the 0.15-μm line pattern obtained by performing thebaking and development immediately after the irradiation of an electronbeam and the 0.15-μm line pattern obtained by performing the baking anddevelopment 3 hours after the irradiation of an electron beam, the linewidth was measured through a scanning electron microscope (S-9220,manufactured by Hitachi Ltd.), and the difference therebetween wasdefined as the in-vacuum PED characteristic.

The results in Example 1 were good, that is, sensitivity; 6.0 μC/cm²,resolving power: 0.11 μm, pattern profile: rectangular, line edgeroughness: 6.0 nm, and in-vacuum PED characteristic: 2.0 nm.

Examples 2 to 16

Preparation of the Resist Solution and Formation of the negative patternwere performed in the same manner as in Example 1 except for usingrespective components shown in Table 1 below. In Table 1, the ratio inusing two or more kinds for a component is the ratio by mass. Theevaluation results are shown in Table 2.

Comparative Example 1

Preparation of the Resist Solution and Formation of the negative patternwere performed in the same manner as in Example 1 except for, as shownin Table 1, not using an organic carboxylic acid as the component (E).The evaluation results are shown in Table 2.

Comparative Example 2

Preparation of the Resist Solution and Formation of the negative patternwere performed in the same manner as in Example 1 except that, as shownin Table 1, a novolak resin not having a repeating unit of formula (1)was used for the resin as the component (A). The evaluation results areshown in Table 2.

Comparative Examples 3 and 4

Preparation of the Resist Solution and Formation of the negative patternwere performed in the same manner as in Example 1 except for, as shownin Table 1, using only a known nitrogen-containing organic basiccompound without using a quaternary ammonium salt as the component (D).The evaluation results are shown in Table 2.

TABLE 1 Cross- Acid Organic linking Generator Ammonium Carboxylic Agentas as Salt as Acid as Exam- Resin as Component (A) Component ComponentComponent Other Component Solvent Surfactant ple (0.40 g) (B) (C) (D)Components (E) (9.0 g) (0.001 g) 1 (29) Mw = 9200 MM-1 C-1 D-1 E-1 S-1W-1 x/y = 80/20 Mw/Mn = 2.0 0.12 g 0.05 g 0.002 g 0.012 g 2 (2) Mw =5000 MM-1 C-1 D-1 E-3 S-1/S-2 = 80/20 W-1 Mw/Mn = 1.18 0.12 g 0.05 g0.002 g 0.012 g 3 (1) Mw = 2500 MM-2 C-2 D-3 E-3 S-1 W-1 Mw/Mn = 1.150.11 g 0.05 g 0.003 g 0.012 g 4 (2) Mw = 7000 MM-3 C-3 D-10 E-3 S-1 W-2Mw/Mn = 1.3 0.12 g 0.05 g 0.004 g 0.012 g 5 (27) Mw = 3500 MM-1 C-2 D-1F-2 E-1 S-1/S-2 = 80/20 W-1 x/y = 85/15 Mw/Mn = 1.2 0.12 g 0.05 g 0.002g 0.002 g 0.012 g 6 (25) Mw = 5000 MM-3 C-2/C-4 = 50/50 D-12 E-3 S-2 W-1x/y = 60/40 Mw/Mn = 1.1 0.12 g 0.05 g 0.006 g 0.012 g 7 (32) Mw = 7500MM-1 C-2 D-2 F-1 E-2 S-1/S-2 = 80/20 W-2 x/y = 80/20 Mw/Mn = 1.6 0.12 g0.05 g 0.002 g 0.002 g 0.012 g 8 (2) Mw = 5000 CL-1 C-4 D-2 E-4 S-1 W-1Mw/Mn = 1.18 0.12 g 0.05 g 0.002 g 0.012 g 9 (2) Mw = 5000 1.1/ MM-1C-2/C-3 = 50/50 D-1 E-3 S-1/S-2 = 80/20 W-1 (1) Mw = 2500 1.1 = 75/250.12 g 0.05 g 0.002 g 0.024 g 10  (58) Mw = 3500 MM-1 C-4 D-1 E-1S-1/S-2 = 80/20 W-1 x/y = 80/20 Mw/Mn = 2.0 0.12 g 0.06 g 0.002 g 0.012g 11  (2) Mw = 5000 MM-1 C-1 D-1 E-1 S-1/S-2 = 80/20 W-1 MW/Mn = 1.180.12 g 0.05 0.002 g 0.012 g 12  (25) Mw = 5000 MM-1 Z-85 D-1 E-1 S-1/S-2= 80/20 W-2 x/y = 60/40 Mw/Mn = 1.1 0.08 g 0.04 g 0.002 g 0.012 g 13 (1) Mw = 2500 Mw/Mn = 1.15 MM-1 Z-85 D-1 E-2 S-1/S-2 = 80/20 W-2 (2) Mw= 5000 Mw/Mn = 1.18 0.08 g 0.04 g 0.002 g 0.012 g (1)/(2) = 25/75 (bymass) 14  (1) Mw = 2500 Mw/Mn = 1.15 MM-1 Z-87 0.02 g D-1 E-1 S-1/S-2 =80/20 W-2 (2) Mw = 5000 Mw/Mn = 1.18 0.08 g Z-88 0.02 g 0.002 g 0.012 g(1)/(2) = 25/75 (by mass) 15  (1) Mw = 2500 Mw/Mn = 1.15 MM-1 Z-87 0.02g D-1 E-1 S-1/S-2 = 80/20 W-2 (2) Mw = 5000 Mw/Mn = 1.18 0.08 g Z-880.02 g 0.002 g 0.012 g (1)/(2) = 25/75 (by mass) 16  (1) Mw = 2500 Mw/Mn= 1.15 MM-1 Z-88 D-1 E-1 S-1/S-2 = 80/20 W-2 (2) Mw = 5000 Mw/Mn = 1.180.08 g 0.04 g 0.002 g 0.012 g (1)/(2) = 25/75 (by mass) Cross- AcidOrganic linking Generator Ammonium Carboxylic Agent as as Salt or Acidas Comparative Component Component Comparative Other Component SolventSurfactant Example Resin (0.40 g) (B) (C) Compound Components (E) (9.0g) (0.001 g) 1 (29) Mw = 9200 MM-1 C-1 D-1 S-1 W-1 x/y = 80/20 Mw/Mn =2.0 0.12 g 0.05 g 0.002 g 2 Novolak Resin AG-2B MM-1 C-1 D-1 E-1 S-1 W-1(produced by Gun Ei 0.12 g 0.05 g 0.002 g 0.012 g Chemical Industry Co.,Ltd.) 3 (25) Mw = 5000 MM-1 C-4 F-3 E-1 S-1 W-1 x/y = 60/40 Mw/Mn = 1.10.12 g 0.05 g 0.004 g 0.012 g 4 (29) Mw = 9200 MM-1 C-1 G-1 E-1 S-1 W-1x/y = 80/20 Mw/Mn = 2.0 0.12 g 0.05 g 0.002 g 0.012 g * When a mixedsolvent is used, the values in the Table indicate the mass ratio.

The abbreviations in the Table are described below.

(Crosslinking Agent)

The acid generators used in Table 1 are as follows.

-   C-1: Triphenylsulfonium nonafluorobutanesulfonate-   C-2: Triphenylsulfonium pentafluorobenzenesulfonate-   C-3; Triphenylsulfonium-2,4-dimethylbenzenesulfonate-   C-4: Bisphenyl-4-cyclohexylphenylsulfonium    pentafluorobenzenesulfonate

The organic carboxylic acids used in Table 1 are as follows.

-   E-1: Benzoic acid-   E-2: 2-Naphthoic acid-   E-3: 2-Hydroxy-3-naphthoic acid-   E-4: o-Hydroxybenzoic acid

Other components used in Table 1 are as follows (all produced by TokyoKasei Kogyo Co., Ltd.).

-   F-1: 2,4,5-Triphenylimidazole-   F-2: 4-Dimethylaminopyridine-   F-3: Triethylamine-   G-1: Trimethylammonium hydrochloride

The solvents used in Table 1 are as follows.

-   S-1: Propylene glycol monomethyl ether acetate-   S-2: Propylene glycol monomethyl ether

The surfactants used in Table 1 are as follows.

-   W-1: PF6320 (produced by OMNOVA)-   W-2: Megafac F176 (produced by Dainippon Ink & Chemicals, Inc.)

TABLE 2 Line Resolv- Pattern Edge In-Vacuum ing Profile Rough- PEDSensitivity Power (rating on 3- ness Character- (μC/cm²) (μm) stagescale) (nm) istic (nm) Example 1 6.0 0.11 rectangular 6.0 2.0 2 5.0 0.10rectangular 5.0 1.7 3 6.0 0.12 rectangular 6.0 2.0 4 7.0 0.12rectangular 6.5 1.8 5 5.0 0.10 rectangular 5.5 1.5 6 6.0 0.13rectangular 7.0 1.6 7 7.0 0.12 rectangular 6.5 1.5 8 6.0 0.14rectangular 7.0 1.9 9 5.0 0.10 rectangular 5.0 1.6 10  5.0 0.10rectangular 5.0 1.8 11  7.0 0.14 rectangular 6.5 1.9 12  7.0 0.12rectangular 6.5 2.0 13  6.0 0.10 rectangular 6.0 1.8 14  5.0 0.10rectangular 5.5 1.7 15  6.0 0.11 rectangular 6.0 1.6 16  5.0 0.11rectangular 6.0 1.8 Comparative Example 1 6.0 0.22 eroded 7.0 2.3 2 10.00.20 slightly 12.5 8.6 eroded 3 8.0 0.18 slightly 10.5 5.6 eroded 4 9.00.18 slightly 11.5 4.3 eroded

It is seen from Table 2 that the negative resist composition of thepresent invention is excellent in terms of sensitivity, resolving power,pattern profile, line edge roughness and in-vacuum PED characteristicand assured of good performance.

According to the present invention, a negative resist compositionexcellent in terms of sensitivity, resolving power, pattern profile,line edge roughness and in-vacuum PED characteristic, and a patternforming method using the composition can be provided.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

1. A negative resist composition, comprising: (A) an alkali-solublepolymer containing a repeating unit represented by formula (1); (B) acrosslinking agent capable of crosslinking with the alkali solublepolymer (A) under an action of an acid; (C) a compound capable ofgenerating an acid upon irradiation with actinic rays or radiation; (D)a quaternary ammonium salt represented by formula (2); and (E) anorganic carboxylic acid:

wherein A represents a hydrogen atom, an alkyl group, a halogen atom ora cyano group; R₁ and R₂ each independently represents a hydrogen atom,a halogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, anaryl group, an aralkyl group, an alkoxy group or an alkylcarbonyloxygroup; and n represents an integer of 1 to 3;

wherein R₃ to R₆ each independently represents an alkyl group, analkenyl group, an aryl group or an aralkyl group; B⁻ represents an OH⁻group, a halogen atom, an R₇—CO₂ ⁻ group or an R₇—SO₃ ⁻ group; and R₇represents an alkyl group, an alkenyl group, an aryl group or an aralkylgroup.
 2. The negative resist composition according to claim 1, whereinthe crosslinking agent (B) is a phenol compound having two or morebenzene rings within a molecular thereof and not containing a nitrogenatom.
 3. A pattern forming method, comprising: forming a resist filmfrom the negative resist composition according to claim 1; and exposingand developing the resist film.
 4. The negative resist compositionaccording to claim 1, wherein the alkali-soluble polymer (A) furthercontains at least one repeating unit selected from the repeating unitsrepresented by formulae (3), (4) and (5):

represents any group selected from the following structures:

wherein A has the same meaning as A in formula (1); X represents asingle bond, a —COO— group, an —O— group or a —CON(R₁₆)— group; R₁₆represents a hydrogen atom or an alkyl group; R₁₁ to R₁₅ eachindependently has the same meaning as R₁ in formula (1); R₁₀₁ to R₁₀₆each independently represents a hydroxy group, a halogen atom, an alkylgroup, an alkoxy group, an alkylcarbonyloxy group, an alkylsulfonyloxygroup, an alkenyl group, an aryl group, an aralkyl group or a carboxygroup; and a to f each independently represents an integer of 0 to
 3. 5.The negative resist composition according to claim 1, wherein thecrosslinking agent (B) is a phenol derivative having a molecular weightof 1,200 or less, containing from 3 to 5 benzene rings within a moleculethereof, and having two or more hydroxymethyl groups or alkoxymethylgroups in total, the two or more hydroxymethyl groups or alkoxymethylgroups being bonded to at least any one benzene ring in a concentratedmanner or distributed among the benzene rings.
 6. The negative resistcomposition according to claim 1, wherein the organic carboxylic acid(E) is at least one selected from the group consisting of a saturated orunsaturated aliphatic carboxylic acid, an alicyclic carboxylic acid, anoxycarboxylic acid, an alkoxycarboxylic acid, a ketocarboxylic acid andan aromatic carboxylic acid.
 7. The negative resist compositionaccording to claim 6, wherein the organic carboxylic acid (E) is atleast one selected from the group consisting of a benzoic acid, a1-hydroxy-2-naphthoic acid and a 2-hydroxy-3-naphthoic acid.